In conventional diesel engines, it is known to inject liquid propane (LPG) into the fuel-air mixture in the fuel header or manifold of the engine. This is done to reduce emissions and increase performance of the vehicle. Typically, the vehicle would include an LPG tank and a pump which is in fluid communication with the LPG tank and pumps the LPG or other fluid into the engine manifold. In a known configuration, such a pump may be an in-tank, submersible turbine pump. However, such a configuration is known to have disadvantages associated therewith.
It therefore is an object of the invention to overcome disadvantages associated with prior art pumps used to deliver liquefied gases.
The invention relates to a fuel supply system for a vehicle, which uses an externally-mounted positive displacement pump to supply the LPG from the storage tank to the engine. More particularly, the invention relates to a dual-acting, seal-less LPG injection pump, which is formed as a piston pump for pumping the fluid from the storage tank to the engine intake manifold. The term seal-less shall refer to a pump that has only stationary seals, and no moving or dynamic seals. In the preferred embodiment, the pump is provided in a dual-acting, single piston configuration, wherein the pump piston is driven by a pneumatic drive actuator which may be formed as a pneumatic drive cylinder or other mechanical drive mechanism that reciprocates the piston. The drive actuator is operated using the vehicle's pneumatic air system, wherein the pressurized air of this system alternatingly drives or reciprocates the pneumatic drive actuator, which in turn drives the piston. The pressure cylinder of the actuator is operatively connected to the pump piston through a seal-less connection, such that movement of one end of the drive cylinder effects a direct, corresponding movement of the piston.
As to the seal-less connection, the inventive pump uses a contained, tubular pump housing, which is formed as a thin-walled pump tube that internally defines a pump chamber. The piston is wholly contained within the elongate pump chamber wherein the piston is driven in a reciprocating manner. Preferably, the piston is dual acting so that each direction of movement defines a pumping stroke. The vehicle's air system is used to pressurize and drive the piston through both pumping strokes.
More particularly, to drivingly connect the pump piston and drive cylinder, an inner magnet set is provided on the piston within the pump chamber, and an outer magnet set is positioned outside of the pump housing adjacent the inner magnet set to form an indirect, magnetic connection through the attractive magnetic fields defined by the magnet sets. Preferably, the tube is made from non-magnetic material, such as stainless steel, but can be constructed from any non-magnetic material. The outer magnet set is carried in a movable main body which in turn is directly connected to the drive cylinder. Reciprocation of the main body also reciprocates the piston due to the magnetic connection therebetween. Since the magnetic connection between the magnet sets requires no penetrations through the pump housing, a seal-less connection is formed between the piston and the drive actuator.
As the main body is moved in one direction, fluid is pumped out of one piston side that is being constricted, which is the outlet side, while fluid is drawn into the opposite suction side of the piston that is being expanded during piston movement, which is the inlet side. When the pneumatic actuator is reversed, pumping action within tube is also reversed, such that the inlet and outlet sides also reverse.
In another aspect of the invention, the pump outlet pressure is a direct result of the motivating input force supplied by the actuator in addition to any inlet pressure supplied to an inlet side of the piston. In the case of high inlet pressures, which can be encountered when pumping a liquefied gas supplied by a pressurized tank, the inlet pressure will assist the pump in reaching higher discharge pressures. Therefore, in the case of a pressurized inlet, a lower motivating force is necessary, which makes the pump more energy efficient.
As a result of the inventive pump design, the alternating operation of the piston generates a continuous, uninterrupted flow of the LPG discharged from the opposite ends of the pump since the piston is always moving through one piston stroke or the other.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.